The technical fields of the present invention are metrology, geodesy and civil engineering. In these arts, Augmented Reality (AR) systems are often utilised for supporting users on a site by referenced visualisations.
Such AR-systems usually comprise at least one marker which is precisely arranged in a pre-defined pose relative to a coordinate system, which an AR-device, such as an AR-helmet, AR-glasses or a tablet/smart phone, may reference itself to by means of the marker. Once locked in (or in other words: “logged” in) into the coordinate system, the AR-device is able to display virtual objects with a precise spatial link to the coordinate system, i.e. to the natural environment. The locked-in-status usually must be maintained continuously by scanning the marker again and again.
When the user is approaching the marker, the field of view of the camera of the AR-device captures less of the environment and at one point, the camera threatens to lose track of the marker. After losing sight of the marker, AR-devices known in the art may still be able to maintain a locked-in-status with help of position and orientation sensors, e.g. an inertial measurement unit (IMU) comprising an accelerometer and/or a gyroscope, or with help of camera image based localisation algorithms. However, such compensatory measures are exposed to accumulation of errors and therefore cannot encounter high precision standards.
Therefore, the invention proposes a situational, temporary high-precision extension of the range of usability of such AR-systems.